Electrical resistor



March 15, 1938. G. E. MEGOW ELECTRICAL RESISTOR Filed July 18,1956

154401144462 5mm? T M 012 Patented Mar. 15, 1938 UNITED STATES ELECTRICAL RESISTOR George. E. Megow, South Milwaukee, as-

signor to Allen-Bradley Company, Milwaukee, Wis., a corporation of Wisconsin Application July 18,

1 Claimf This invention relates to electrical resistor units and refers particularly to fixed resistor units used in radio circuits and especially radio receivers.

Fixed resistors oi this type now generally consist of a molded or lumped body of resistance material with wire leads projecting from the ends thereof by which the unit is connected in the circuit.

Modern radio receivers and particularly those for use in automobiles. have their composite ele ments compacted into small space and the trend is to even greater compactness. Obviously, crowding the parts together in this manner entails special provision for electrical insulation as the clearances between the different parts is ordinarily inadequate.

In keeping with this growing necessity for positive electrical insulation, it is an object of this invention to provide a simple eilicient manner of insulating fixed resistor units of the character described.

Resistor units of this type are color coded to indicate their different values and generally the color code marking is applied directly to the body of the. unit. This marking should be visible at all times and consequently, it is another object of this invention to provide an insulation for resistor units of the character described which is transparent so as not to conceal the color code marking.

A further object of this invention is to provide means for insulating resistor units which affords a degree of protection against moisture and which adds to the mechanical strength of the unit and provides protection against obliteration of the color code marking.

While adequate-insulation and transparency are of primary importance, low cost is also an important consideration, and consequently it is another object of this invention to provide an insulatlng enclosure for lumped resistor which is made of inexpensive material easily formed and applied.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claim, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claim.

'I'he accompanying drawing illustrates seven complete examples of the physical embodiment 1936, Serial No. 91,305

(01;. col -cs) of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

Figures 1 to '7, inclusive, are perspective views of resistor units illustrating several different embodiments of this invention;

Figure 8 is a cross section view through Figure l, on the plane of the line 8-8; and

Figure 9 is a cross section view through Figure l, on the plane of the line 9-4.

Referring now particularly to the accompanying drawing, the numeral 5 designates the body of a lumped resistor unit which is preferably cylinclrical with an outer cylindrical wall 6 and end walls l. Projecting from the ends of the body are who leads 8 by which the unit is connected in an electrical circuit.

To indicate the resistance value of the unit and possibly also its plus or minus tolerance, bands 9 of difierent color combinations are applied directly to the cylindrical Wall S of the body.

To attain the objects of thisinvention by providing an insulating covering which Will be transparent so as not to conceal the color code marking and at the same time afford adequate electrical insulation and a degree of protection against moisture, the body of the unit and pre1ferably a substantial portion of its leads 8 are encased in a shell or casing ill of transparent material having the desired characteristics. This shell or casing it may be applied in. any of a number of different ways and in Figure 1 the shell is in the form of a tube slipped over the resistor unit with its end portions extending out over the Wire leads and twisted as at it so as to closely engage the leads and thereby hold itself onto the unit.

The shell or casing may be composed of anyone of a number of different substances, preferably some transparent organic film such as Cellophane", Pliofllm, a cellulose acetate and modified' forms thereof, a cellulose nitrate and modifled forms thereof, or any other synthetic resin film.

Cellophane as is well known is a cellulose product, and Pliofilm is a chlorinated rubber product.

The casing or shell may fit the body of the resistor snugly or loosely as shown in Figures 1 r and 8. With certain types of material, especially Cellophane, a loose fit is preferable as this material unless specially treated will he electrically conductive after being subjected to humidity, if it is fitted closely to the unit, whereas, if a fitted loosely, it is free from this defect. Pliofilm on the other hand will not conduct electrically whether it is fitted to the unit tightly or loosely.

Obviously, the casing or shell may be formed in many different ways. In Figure 2, it is built up by winding a ribbon l2 of the desired transparent material continuously and progressively over the wire leads and the body 0! the unit as shown.

If desired, only the body of the unit is covered with the insulating shell, and in Figures 3, 4, and 5, different ways in which this may be done are shown.

In Figure 3, an insulating and protecting shell is formed by winding a ribbon of the desired material onto the unit.

In Figure 4, a tube l3 slightly longer than the length of the unit is closely fitted to the body. Where this method is employed, it is preferable to use a substance other than Cellophane as it entails a tight close fit.

In Figure 5, a sleeve l4 closely fitted to the body as in Figure 4 has its end portions crimped or pressed down against the end walls I of the body as at I5 to add to the protection afiorded by the covering.

- The advantages of the invention are also capable of realization by merely slipping a tube i6 of suitable transparent insulating material over the unit with its end portions projecting out over the wire leads without specific provision for holding the same in place.

In theembodiment of the invention shown in Figure 7, protection against moisture is particularly obtained. In this modification, the protecting shell consists of two telescoped sleeves l1 and I8 pushed onto the unit from opposite ends thereof and with their adjacent open ends overlapping as at IS. The outer ends of the sleeves are reduced in diameter and have end portions 2' ,to closely hug the wire leads and thereby insure the greatest protection against the entrance of moisture.

Inasmuch as the end portions 20 frictionally engage the wire leads, no other means need be provided to hold the enclosing shell on the unit and the sleeves need not fit the body closely. However, if desired, the overlapping ends of the sleeves may be fused together or a juncture may be formed therebetween by merely bringing the inner ends of the sleeves into abutting relation and then forming a fused juncture therebetween.

From the foregoing description taken in connection with the accompanying drawing, it will be readily apparent to those skilled in this art that this invention in all of its various modifications provides a simple and efilcient manner. of electrically insulating fixed resistor units, and that in each instance, the desired insulation is obtained without concealing the color code marking of the unit and without in anywise complicating the design or construction 01' the unit and at a minimum cost.

What I claim as my invention is:

An insulated electrical resistor comprising: a lumped resistor body; wire leads projecting from opposite ends thereof; and an insulating covering for the body and its leads, said covering being composed of a thin transparent cellulose material and fitting the body loosely so as to provide an air space between the body and the covering, and the ends of the covering being fitted closely to the Wire leads.

GEORGE E. MEGOW. 

